It is known to provide a fuel system for a vehicle having a fuel tank to hold fuel to be used by an engine of the vehicle. It is also known to provide an evaporative emission system for a fuel system of the vehicle to recover fuel vapor. Typically, the evaporative emission system includes a vapor canister remotely mounted such as in an engine compartment of the vehicle and operatively connected by separate external valves and lines to a fuel tank.
Typically, purge solenoid valves are operated between manifold vacuum and pressure of the evaporative emission system, which is approximately atmospheric pressure. However, this allows the highest purge flows at low engine airflows and the lowest purge flow at the highest engine airflows, which is undesired.
Therefore, it is desirable to provide a purge flow more proportional to engine airflow for an evaporative emission system of a vehicle. It is also desirable to provide a variable metering or purge orifice for purge flow in an evaporative emission system of a vehicle. It is further desirable to provide a variable metering or purge orifice that allows a flow rate of a purge solenoid to be increased without losing low flow resolution.